A system and a method for detecting moisture comprising a cable, a cable for detecting moisture and a moisture detection device

ABSTRACT

A moisture detection system (100) comprises a cable (102), a voltage regulator (104) and a differential amplifier (106). The cable (102) comprises an elongated non-conductive moisture permeable structure (108), a first elongated lead (110) and a second elongated lead (112). The first and second leads (110, 112) are substantially equal in length and are connected to the differential amplifier (106) and arranged such that they are not in galvanic contact with each other at any location along the cable (102). The voltage regulator (104) is configured to supply a regulated voltage to the first lead (110) and to the differential amplifier (106). The differential amplifier (106) is configured to determine a voltage difference between the first and second leads (110, 112), and configured to provide a signal that is representative of the determined voltage difference.

TECHNICAL FIELD

Embodiments herein relate to systems, arrangements and methods fordetection of moisture.

BACKGROUND

Damage to property due to undesired presence of liquids, for example asa consequence of a leaking water pipe or leaking machinery, is a commonproblem in many types of environments, private as well as industrial.Needless to say, it is important to minimize such damages and the costsassociated with the damages. This may of course be done by making everyeffort to prevent the leaks from occurring in the first place. But,nevertheless, having occurred anyway it is desirable to obtain an early,reliable and unambiguous detection of the leak.

Moreover, although leaks in the form of liquid may be very damaging,moisture in high humidity situations may also be undesirable. Dependingon parameters such as temperature and pressure, moisture occurs whenhumid gas condenses. Even if the amount of condensed liquid may belimited in comparison with an amount of liquid flowing from a leakingpipe or vessel, it is nevertheless desirable to obtain an early,reliable and unambiguous detection of moisture even though its presenceis not due to a leak.

Prior art moisture detection arrangements include a fluid detectioncable as described in U.S. Pat. No. 6,144,209, where elongatedconductive members are located in grooves along an elongated and twistednon-conductive flexible base member. The conductive members are coatedwith a non-conductive water-insoluble liquid pervious coating. The cableis connected to a control system that generates an alarm when fluid getsin contact with the conductive members.

Drawbacks with such a cable include mechanical limitations such asstiffness that makes it difficult to arrange the cable in full contactwith a floor surface.

The prior art also includes liquid permeable coaxial cables. For examplea coaxial cable where a central conductor is covered by a layer ofisolating yarn, which in turn is covered by a braided screen of mixedconductor and polyester yarns and an outermost braiding of polyesteryarn.

Although such prior art moisture detection arrangements are able todetect moisture to some extent, there remain drawbacks that needattention, for example regarding untimely, unreliable and ambiguousmoisture detection.

SUMMARY

In view of the above, an object of the present disclosure is to overcomeor at least mitigate at least some of the drawbacks related to prior artmoisture detection arrangements.

This is achieved in a first aspect by a moisture detection system thatcomprises a cable, a voltage regulator and a differential amplifier. Thecable comprises an elongated non-conductive moisture permeablestructure, a first elongated lead and a second elongated lead. The firstand second leads are substantially equal in length and are connected tothe differential amplifier and arranged such that they are not ingalvanic contact with each other at any location along the cable. Thevoltage regulator is configured to supply a regulated voltage to thefirst lead and to the differential amplifier. The differential amplifieris configured to determine a voltage difference between the first andsecond leads, and configured to provide a signal that is representativeof the determined voltage difference.

In other words, such a system enables moisture detection by the factthat, when the cable is subjected to moisture there will run an electriccurrent through the two leads. Depending on what kinds of molecules arepresent in the moisture, this current will vary in size. In any case,disregarding any absolute value of the current, the current will resultin a voltage drop from the first lead to the second lead. Since theleads are connected to the differential amplifier, the signal providedby the differential amplifier will be representative of the voltage dropbetween the two leads and therefore also representative of the moisture.This is advantageous in that it is a simple system and thereby easy andcheap to produce. Due to the fact that a differential amplifier is verysensitive to voltage differences, early detection of even small amountsof moisture is possible.

Moreover, due to the fact that the two leads are of equal length, anyexternal influence from electric fields from, e.g., electric machinery,power cables and fluorescent lamps will affect both leads in a similarmanner. As a consequence, there will be no electric potential differencebetween the two leads due to external electric fields. An advantage ofthis is that the moisture detection will be both reliable andunambiguous. That is, when the differential amplifier produces a signal,it is certain that the signal is due to a moist cable and not due to anexternal electric field present at the location of the cable. Needlessto say, this is a common situation, not least in an environment withelectric machinery, power cables and fluorescent lamps. This is incontrast to prior art moisture detection systems not using differentialamplifiers. Typically, such prior art systems are therefore verysensitive to external electric fields and thereby are unable to achievethe advantages of the system of the present disclosure.

In some embodiments, the regulated voltage is in the form of constantvoltage pulses having a duration DT1 and a repetition interval DT2. DT2is greater than DT1 and, preferably, DT2 is at least one order ofmagnitude greater than DT1.

In other words, in these embodiments the regulated voltage is pulsedwith duration DT1 and repeated every DT2. When moisture is present inthe cable there will run an electric current through the cable and othercircuitry in the system. By supplying such a pulsed regulated voltagethe amount of electric energy used can be reduced. For example, in acase where the voltage regulator takes electric energy from a voltagesource that is a battery an advantage of having a pulsed regulatedvoltage is that the battery life span can be increased.

In some embodiments, the voltage regulator and the differentialamplifier are configured to receive pulses of unregulated voltage V1from a voltage supply. The pulses of unregulated voltage V1 have theduration DT1 and the repetition interval DT2.

That is, in such embodiments, also the differential amplifier isprovided with voltage in a pulsed manner and therefore minimizing theamount of use of energy from the voltage supply. This is particularlyadvantageous in a scenario where energy is provided to the system from abattery.

In some embodiments, the first elongated lead and the second elongatedlead have a substantially constant distance from each other along thecable.

That is, such a configuration of the two leads will ensure that thecable will have a constant detection sensitivity to moisture along thelength of the cable, This means that a specific amount of moisture willresult in a specific representative signal provided by the differentialamplifier, irrespective of at which position along the cable thespecific moisture is located. In other words, such a configurationprovides an unambiguous detection of moisture.

In some embodiments, the elongated non-conductive moisture permeablestructure comprises a first braid of yarn and the first and secondelongated leads are braided within the first braid of yarn. In some ofthese embodiments, the elongated non-conductive moisture permeablestructure comprises a second braid of yarn arranged concentric withrespect to, and covering, the first braid of yarn.

That is, by utilizing braided yarns it is possible to provide a cablethat is very flexible and adaptable to any surface it is arranged at.For example, when arranged on a floor, the braided structure will enablethe whole length of the cable to fall into contact with the floorwithout undesirable kinks that may cause the cable to be above thefloor. An advantage of this is that moisture can be reliably detected bythe system.

Furthermore, an advantage of utilizing braided yarn is that the twoelongated leads may be easily incorporated into the first braid of yarnduring a manufacturing process. That is, remembering that a braidingapparatus utilizes a plurality of rolls of yarn that are braided into abraid: by replacing two of the rolls of yarn with a respective first anda second roll of electric lead, little or no modification to thebraiding apparatus or the actual braiding procedure is required.

The system may further be embodied as described in more detail below.

In another aspect there is provided a cable for detecting moisture. Thecable comprises an elongated non-conductive moisture permeablestructure, a first elongated lead and a second elongated lead. The firstand second leads are substantially equal in length and arranged suchthat they are not in galvanic contact with each other at any locationalong the cable. The first and second leads are also configured to beconnected to a voltage regulator and to a differential amplifier.

In a further aspect there is provided a moisture detection device thatcomprises a voltage regulator, a differential amplifier and a controlunit. The control unit comprises a processor, a memory and communicationcircuitry. The voltage regulator is configured to supply a regulatedvoltage to the differential amplifier and to a first lead of a cable assummarized above. The differential amplifier is configured to determinea voltage difference between the first lead of the cable and a secondlead of the cable, and configured to provide a signal that isrepresentative of the determined voltage difference to the control unit.The control unit is configured to process the signal and configured to,as a result of the processing of the signal, perform a moisturedetection related action. In yet another aspect there is provided amethod performed by a control unit for detecting moisture. The controlunit is connected to a system as summarized above and the methodcomprises:

-   -   controlling the voltage regulator to supply a regulated voltage        to the first lead and to the differential amplifier,    -   receiving a signal that is representative of a determined        voltage difference,    -   process the signal, and    -   performing, as a result of the processing of the signal, entity        moisture detection related action.

These further aspects can be embodied, and have technical effects andadvantages, that correspond to those summarized above in connection withthe system for detecting moisture and further embodied as described inmore detail below.

The expressions “substantially equal” and “substantially constant” usedherein are to be interpreted in the respective context in which theyoccur. For example, “substantially equal” means that entities are equalwithin a typical manufacturing error or measurement error in therespective context.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates a block diagram of a system formoisture detection,

FIG. 2 schematically illustrates a block diagram of a moisture detectiondevice,

FIGS. 3a and 3b are schematically illustrated cross-sectional views of acable,

FIG. 4 is a schematically illustrated combined block and circuit diagramof a system for moisture detection,

FIGS. 5a-c are schematically illustrated voltage diagrams in a systemfor moisture detection, and

FIG. 6 is a flowchart of a method performed in a control unit in asystem for moisture detection.

DETAILED DESCRIPTION

Referring first to FIG. 1, a system 100 for detecting moisture comprisesa cable 102, a voltage regulator 104 and a differential amplifier 106. Acontrol unit 120 is configured to interact with the system 100, as willbe exemplified below. The cable 102 comprises an elongatednon-conductive moisture permeable structure 108, a first elongated lead110 and a second elongated lead 112. The first and second leads 110, 112are substantially equal in length and connected to the differentialamplifier 106. The first and second leads 110, 112 are arranged suchthat they are not in galvanic contact with each other at any locationalong the cable 102.

The voltage regulator 104 is configured to supply a regulated voltageVreg to the first lead 110 and to the differential amplifier 106. AsFIG. 1 exemplifies, a voltage supply 114 such as a battery or any othersuitable energy source may be connected to the system 100 in order toprovide necessary electric energy to the system 100, including thevoltage regulator and other circuitry such as the differential amplifier106.

The differential amplifier 106 is configured to determine a voltagedifference between the first and second leads 110, 112, and it is alsoconfigured to provide a signal VD that is representative of thedetermined voltage difference between the two leads 110, 112.

While the regulated voltage Vreg is supplied to the first lead 110 andwhile the cable 102 is subjected to moisture there will run an electriccurrent through the two leads 110, 112. Depending on what kinds ofmolecules are present in the moisture, this current will vary in sizedue to the fact that the impedance between the leads varies with themoisture level. In any case, disregarding any absolute value of thecurrent, the current will result in a voltage drop from the first lead110 to the second lead 112. Since the leads 110, 112 are connected tothe differential amplifier 106 the signal VD provided by thedifferential amplifier 106 will be representative of the voltage dropbetween the two leads 110, 112 and therefore also representative of themoisture.

For example, as will be appreciated when considering the combined blockand circuit diagram in FIG. 4, in case the cable 102 is relatively dry,the voltage drop will be relatively large and in case the cable 102 isrelatively moist, the voltage drop will be relatively small.Corresponding output signals VD provided by the differential amplifier406 will be relatively large and small, respectively.

In FIG. 4, a voltage supply 414 provides a feeding voltage V1 to avoltage regulator 404 and to a differential amplifier 406. The feedingvoltage V1 may be an unregulated and hence varying voltage, e.g. as aconsequence of the voltage supply 414 being a battery that is beingdrained. A switch 440 is controlled by a control voltage VC to providethe unregulated feeding voltage V1 to both the voltage regulator 404 andto the differential amplifier 406. The control voltage VC may forexample provided by a control unit (not shown in FIG. 4) such as thecontrol unit 120 in FIG. 1 and FIG. 2 to be described below. The voltageregulator 404 is configured to regulate the feeding voltage V1 andprovide the regulated voltage Vreg to a first elongated lead 410 in thecable 402 and to a first input 450 on the differential amplifier 406 viaan impedance unit that in FIG. 4 is denoted a second impedance unit Z2.

A second elongated lead 412 is connected to a second input 451 on thedifferential amplifier 406. An impedance unit that in FIG. 4 is denoteda first impedance unit Z1 connects the second lead 412 and the secondinput 451 to ground. Depending on the level of moisture in the cable402, an impedance Zcable will be present between the two leads 410, 412and, given the regulated voltage Vreg, a voltage difference VB-VA at theinputs 450, 451 of the differential amplifier 406 will have a value thatdepend on the values of Vreg, Z1, Z2 and the impedance Zcable (i.e.moisture) of the leads 410, 412 in the cable 402.

In some embodiments, the configuration of the impedance units Z1 and Z2are such that they have substantially equal impedance values. Suchembodiments have the advantage that the so-called “common mode”interference, i.e. interference received by the two leads 410, 412 fromexternal electric fields can be suppressed to a very large extent. Thisadvantage is further accentuated in that the two leads 410, 412 aresubstantially equal ion length.

As is evident from FIG. 4, details regarding the internal structure ofthe differential amplifier 406 are known to the skilled person and suchdetails will not be described herein for the sake of clarity.

As exemplified in FIG. 5a , the regulated voltage Vreg may be in theform of constant voltage pulses having a duration DT1 and a repetitioninterval DT2, where DT2 is greater than DT1. For example, DT2 may be atleast one order of magnitude greater than DT1. A larger ratio betweenDT2 and DT1 will result in a relatively smaller energy consumption fromthe voltage supply 414 and, vice-versa, a smaller ratio between DT2 andDT1 will result in a relatively larger energy consumption from thevoltage supply 414. These constant voltage pulses having the voltageVreg may be formed by means of the switch 440 controlled by a controlunit as indicated above.

The voltage regulator 404 and the differential amplifier 406 may beconfigured to receive pulses of the unregulated voltage V1 from thevoltage supply 414. In such embodiments, the pulses of unregulatedvoltage V1 may have the duration DT1 and the repetition interval DT2.This is advantageous because also the differential amplifier 406contributes to minimizing the consumption of energy by the fact that itis in operation only during the same time intervals, i.e. during therepeated DT1 durations, as the rest of the circuitry of the system.

It is to be noted that the example of FIG. 5a , is not an indicationthat DT1=100 μs and DT2=1 s is a preferred DT2/DT1 configuration. Theskilled person will apply suitable values on DT1 and DT2 in order toachieve a desired energy consumption while at the same time achieve adesired time resolution of the voltage pulses that provides a desiredtime resolution of the moisture detection.

Referring back to the discussion above in relation to FIG. 4 and withreference to FIG. 5b and FIG. 5c , FIG. 5b illustrates a signal VD 503that is relatively large and FIG. 5c illustrates a signal VD 505 that isrelatively small. The VD signals 503, 505 have a maximum level thatdepend on the regulated voltage Vreg as well as the resistive part ofthe impedances Zcable, Z1 and Z2. That is, remembering the descriptionof the circuit in FIG. 4, FIG. 5b may be seen as exemplifying that thecable 102, 402 is relatively dry and FIG. 5c may be seen as exemplifyingthat the cable 102, 402 is relatively moist.

In FIGS. 5b and 5c , a detection voltage threshold 511 and a hysteresisthreshold 512 are illustrated. Such thresholds 511, 512 may be utilizedin a control unit, e.g. such as the control unit 120 discussed above inconnection with FIG. 1, during an analysis of the signal VD in order todetermine whether there is moisture or not at a location where the cable102, 402 is located. For example, such an analysis may include adecision to provide a warning of moisture as long as the signal VD isbelow the detection threshold 511 and provide information that themoisture level has been reduced when the signal VD is above thehysteresis threshold 512.

With reference to the cable 102 and cable 402, schematically illustratedin FIGS. 1 and 4 respectively, the first elongated lead 110, 410 and thesecond elongated lead 112, 412 may have a substantially constantdistance from each other along the cable 102, 402. As mentioned above,such a configuration of the two leads 110, 410, 112, 412 will ensurethat the cable 102, 402 will have a constant detection sensitivity tomoisture along the length of the cable 102, 402.

Turning now to FIG. 3a and FIG. 3b , embodiments of a cable 302 will bedescribed. The cable 302 may correspond to the cable 102, 402 describedabove in connection with FIGS. 1 and 4, respectively. For example, theelongated non-conductive moisture permeable structure 108, 408 maycomprise a first braid of yarn 331 and in such embodiments, a firstelongated lead 310 and a second elongated lead 312, corresponding to theleads 110, 410, 112, 412 described above, are braided within said firstbraid of yarn 331. In some of these embodiments of the cable 302, theelongated non-conductive moisture permeable structure 108, 408 maycomprise a second braid of yarn 332 arranged concentric with respect to,and covering, the first braid of yarn 331.

An effect of the second braid of yarn 332 is that it protects the twoleads 310, 312 from unintentional contact with a surface on which thecable 302 is located. Such unintentional contact between leads 310, 312and surface may otherwise result, in a worst case, in an electricshort-circuit with corresponding deterioration or even a malfunction ofthe moisture detection.

In some embodiments, the cable 302 may comprise a glass yarn 334arranged concentric with and covered by the first and second braids ofyarn 331, 332. In some of these embodiments, the glass yarn 334 may becovered by an insulating layer 333. An effect of such embodiments isthat the thickness and mechanical stability of the cable 302 may beincreased. For example, an appropriately woven glass yarn 334 with anappropriately chosen thickness of the insulating layer 333 may providethe cable 302 with an appropriate flexibility and weight-to-length ratiothat makes the cable 302 easy to lay down on a floor surface whilemaking sure that the whole length of the cable 302 is in contact withthe floor surface. An example of dimensions are as follows: glass yarn334 having a diameter of 0.8 mm, covered by the insulating layer 333 upto a diameter of 2.0 mm, covered by the first braid of yarn 331 up to adiameter of 2.6 mm, covered by the second braid of yarn 332 up to atotal diameter of 3.2 mm.

Any of the first braid of yarn 331 and the second braid of yarn 332 maycomprises any of the materials polyester, polypropylene, nylon, textile,cotton, rayon and Kevlar. Moreover, the glass yarn 334 may be replacedby any suitable yarn or other string that provides correspondingmechanical strength to the cable 302.

As exemplified in FIG. 3b , the cable 302 may have any cross-sectionalshape including a flat shape. Depending on which technique is used inbraiding the yarns of the first and second braids 331, 332, anydesirable cross-sectional shape may be obtained, fitting any specificspatial and mechanical requirement relating to the environment in whichthe cable 302 is to be installed.

In some embodiments, the elongated non-conductive moisture permeablestructure 108, 408 may, instead of the braids of yarn described above,comprise any of a moisture permeable molded material and a moisturepermeable filler material. For example, a molded material or fillermaterial may have perforations (natural or machined) that allow moistureto get in contact with the two leads whereby the cable provides themoisture detection as described above. Examples of such molded andfiller material include plastics such as PVC and polyethylene, foamedand fibrillated polypropylene, cotton and rayon as well as Kevlar.

In some embodiments, the two leads 310, 312 may be coated with anon-conductive, and in a liquid insoluble, moisture pervious coating(not illustrated in FIGS. 3a and 3b ). Such a coating may be very thinand it would fill the purpose of additional protection againstinadvertent contact between the leads 310, 312 and between any externalsurface or arrangement that potentially could cause a short-circuit.Such a coating may also help to prevent corrosion on the two leads 310,312.

FIG. 2 illustrates an example of a moisture detection device 200 thatcomprises a voltage regulator 104 and a differential amplifier 106. Asindicated by the reference numerals, these units 104, 106 may correspondto similar parts of the system 100 described above. The device 200further comprises a control unit 120 that comprises a processor 122, amemory 124 and communication circuitry 126. A voltage supply 114 mayalso be part of the device 200.

As in the system 100 described above, the voltage regulator 104 isconfigured to supply a regulated voltage Vreg to the differentialamplifier 106 and to a first lead of a cable 102. The cable 102 maycorrespond to any of the cables described above.

As in the system described above, the differential amplifier 106 isconfigured to determine a voltage difference between the first lead ofthe cable 102 and a second lead of the cable 102, and configured toprovide a signal that is representative of the determined voltagedifference to the control unit 120.

The control unit 120 is configured to process the signal provided fromthe differential amplifier 106 and configured to, as a result of theprocessing of the signal VD, perform a moisture detection relatedaction.

In some embodiments, the action that is performed as a result of theprocessing of the signal VD may comprise providing the signal VD to areceiving entity 210 where it may be further analyzed and acted upon.Such a provision of the signal to the receiving entity 210 may beperformed via the communication circuitry 126, which circuitry 126 maybe in the form of a wireless communication circuit as well as in theform of a wired communication circuit, for example utilizing appropriatecommunication standard specified protocols and interfaces as the skilledperson will realize.

Alternatively, the signal VD may remain in the device 200 and themoisture detection related action may in such a case entail furtheranalysis in terms of moisture detection or, even simpler, providing awarning signal for alerting a user to the fact that the device 200 hasdetected moisture.

In some embodiments, the signal VD may remain locally in the device 200for some time and also be analyzed locally by the processor 122whereupon information resulting from such analysis may be provided tothe receiving entity 210 for further action and, e.g., recording.

Turning now to FIG. 6, a method performed by a control unit will bedescribed. The control unit that performs the method is in this examplethe control unit 120 that is connected to the system 100 as describedabove in connection with FIGS. 1 to 5. The method is illustrated in theform of a flowchart comprising a number of actions that are performedfor detecting moisture. The actual execution of the various actions bythe control unit is realized by way of software instructions stored in amemory and executed by a processor, e.g. the memory 124 and processor122 in the control unit 120. The actions are as follows:

Action 601

The voltage regulator 104, 404 is controlled to supply a regulatedvoltage Vreg to the first lead 110, 310, 410 and to the differentialamplifier 106, 406.

The regulated voltage Vreg may be in the form of constant voltage pulseshaving a duration DT1 and a repetition interval DT2. DT2 is greater thanDT1 and, preferably, DT2 is at least one order of magnitude greater thanDT1. Such pulses may be formed by the control unit 120 by controllingprovision of electric energy from a voltage supply to the voltageregulator 104, 404 and, in some embodiments also to the differentialamplifier 106, 406, via a simple switch, e.g. the switch 440 asdescribed above in connection with FIG. 4.

Action 603 A signal VD that is representative of a determined voltagedifference is received. As described above, the signal VD is receivedfrom the differential amplifier 106, 406 and the voltage difference is avoltage difference between the first lead 110, 310, 410 and a secondlead 112, 312, 412 comprised in the cable 102, 302, 402.

Action 605

The received signal VD is processed. This processing may involve more orless complex operations. For example, a relation may be assumed, asbriefly discussed above, that a small VD level may be mapped to a highlevel of moisture and a high VD level may be mapped to a low level ofmoisture. However, the VD signal may also be processed in a very minimalmanner in that it remains as a voltage level.

Action 607

As a result of the processing in action 605 a moisture detection relatedaction may be performed.

In some embodiments, the action that is performed as a result of theprocessing of the signal VD may comprise providing the signal VD to areceiving entity 210 where it may be further analyzed and acted upon.For example, the provision may involve transmission via a wired orwireless communication network to a user or a central server etc. wherethe information may be stored, further analyzed and presented in asuitable manner.

Alternatively, the signal VD may remain in the device 200 and themoisture detection related action 607 may in such a case entail furtheranalysis in terms of moisture detection or, even simpler, providing awarning signal for alerting a user to the fact that the device 200 hasdetected moisture.

In some embodiments, in action 607, the signal VD may remain locally inthe device 200 for some time and also be analyzed locally by theprocessor 122 whereupon information resulting from such analysis may beprovided to the receiving entity 210 for further action and, e.g.,recording.

1-20. (canceled)
 21. A system for detecting moisture, comprising: acable comprising an elongated non-conductive moisture permeablestructure, a first lead, and a second lead, the first and second leadsbeing substantially equal in length and arranged such that they are notin galvanic contact with each other at any location along the cable; adifferential amplifier connected to the first and second leads andconfigured to determine a voltage difference between the first andsecond leads, and to provide a signal that is representative of thedetermined voltage difference; and a voltage regulator configured tosupply a regulated voltage to the first lead and to the differentialamplifier; wherein the elongated non-conductive moisture permeablestructure comprises a first braid of yarn, and wherein the first leadand the second lead are braided within the first braid of yarn.
 22. Thesystem of claim 21 wherein the voltage regulator is configured such thatthe regulated voltage is provided via a second impedance unit to thefirst lead and to a first input on the differential amplifier; andwherein the second lead is connected to a second input on thedifferential amplifier, and is connected to ground via a first impedanceunit.
 23. The system of claim 22, wherein the first impedance unit andthe second impedance unit have substantially equal impedance values. 24.The system of claim 21, wherein the regulated voltage is in the form ofconstant voltage pulses having a duration DT1 and a repetition intervalDT2, where DT2 is greater than DT1.
 25. The system of claim 24, whereinDT2 is at least one order of magnitude greater than DT1.
 26. The systemof claim 24, wherein the voltage regulator and the differentialamplifier are configured to receive pulses of unregulated voltage from avoltage supply, the pulses of unregulated voltage having the durationDT1 and the repetition interval DT2.
 27. The system of claim 21, whereinthe first lead and the second lead have a substantially constantdistance from each other along the cable.
 28. The system of claim 21,wherein the elongated non-conductive moisture permeable structurecomprises a material selected from the group consisting of a moisturepermeable molded material and a moisture permeable filler material. 29.The system of claim 21, wherein the elongated non-conductive moisturepermeable structure comprises a second braid of yarn that is concentricwith respect to, and covers, the first braid of yarn.
 30. The system ofclaim 29, wherein at least one of the first braid of yarn and the secondbraid of yarn comprises a material selected from the group consisting ofone or more of polyester, polypropylene, nylon, textile, cotton, rayon,and Kevlar.
 31. The system of claim 29, wherein the cable comprises aglass yarn that is concentric with and covered by the first and secondbraids of yarn.
 32. The system of claim 31, wherein the glass yarn iscovered by an insulating layer.
 33. A cable for detecting moisture,comprising: an elongated non-conductive moisture permeable structure, afirst lead, and a second lead, the first and second leads beingsubstantially equal in length and arranged such that they are not ingalvanic contact with each other at any location along the cable;wherein the elongated non-conductive moisture permeable structurecomprises a first braid of yarn, and wherein the first lead and thesecond lead are braided within the first braid of yarn.
 34. The cable ofclaim 33, wherein the first lead and the second lead have asubstantially constant distance from each other along the cable.
 35. Thecable of claim 33, wherein the elongated non-conductive moisturepermeable structure comprises a material selected from the groupconsisting of a moisture permeable molded material and a moisturepermeable filler material.
 36. The cable of claim 33, wherein theelongated non-conductive moisture permeable structure comprises a secondbraid of yarn that is concentric with respect to, and covers, the firstbraid of yarn.
 37. The cable of claim 36, wherein at least one of thefirst braid of yarn and the second braid of yarn comprises a materialselected from the group consisting of one or more of polyester,polypropylene, nylon, textile, cotton, rayon, and Kevlar.
 38. The cableof claim 36, wherein the cable comprises a glass yarn that is concentricwith and is covered by the first and second braids of yarn.
 39. Thecable of claim 38, wherein the glass yarn is covered by an insulatinglayer.
 40. A moisture detection device comprising: a differentialamplifier; a control unit operatively connected to the differentialamplifier; a cable having a first lead and a second lead, the first leadand the second lead being of substantially equal length, and arranged sothat they are not in galvanic contact with each other at any locationalong the cable; and a voltage regulator configured to supply aregulated voltage to the differential amplifier and to the first lead ofthe cable; wherein: the differential amplifier is configured todetermine a voltage difference between the first lead of the cable andthe second lead of the cable, and to provide a signal that isrepresentative of the determined voltage difference to the control unit;the control unit includes a processor that is configured to process thesignal and, as a result of the processing of the signal, to perform amoisture detection related action; the cable comprises an elongatednon-conductive moisture permeable structure that comprises a braid ofyarn; and the first lead and the second lead are braided within thebraid of yarn.